Cataract surgeries are the most commonly performed surgeries on the human eye and are therefore in the focus of continuous improvements or of the quality of the surgery result, efficiency in the surgery execution and minimization of risk. Through recent developments and progresses in ophthalmic femtosecond (fs) laser technology, especially in the area of refractive eye surgery, and of optical coherence tomography (OCT) as imaging technology, cataract surgeries are increasingly automated. Hereby, short pulse lasers are used to “cut” the eye tissue by application of photodisruption. This technology is hereinafter referred to as laser-assisted cataract surgery (LCS). According to current application principles, capsulotomy (circular incision of the anterior capsular bag of the eye lens), lens fragmentation (dividing the eye lens nucleus), access cuts in the cornea (main access and auxiliary cuts), and arcuate incisions (circular cuts for reducing a corneal astigmatism) are carried out within the scope of LCS, wherein the latter significantly goes beyond the extent of the classic cataract surgery, and touches the area of refractive eye surgery.
In U.S. Pat. No. 6,325,792 B1 it is suggested to focus pulses of a femtosecond laser into the eye lens in order to “liquefy” the eye lens—this corresponds to the abovementioned lens fragmentation—or to cut the capsulotomy. The positioning of the pulse focuses of the femtosecond laser thereby takes place by the use of ultrasonic imaging.
In U.S. Pat. No. 5,246,435 it is disclosed to focus pulses of a short pulse laser in a three-dimensional incision pattern into the natural lens of the eye, to separate the lens into fragments by application of the cuts and liquefy it thereby.
In U.S. Pat. No. 6,454,761B1 it is suggested to use the optical coherence tomography (OCT) instead of ultrasound imaging for the automatic positioning of laser pulses in eye surgery operations on the cornea or other transparent structures, e.g. when removing a cataract in the eye lens.
Only a few years ago, the increasing maturity of the femtosecond laser technology and of the OCT technology permitted a combination and integration of these two technologies and the establishment of largely automated femtosecond laser systems in cataract surgery. For deflecting the femtosecond pulses, fixed objectives and fast mirror scanners for the lateral x/y-deflection of the laser beam in the eye are used on the one hand and slowly adjustable lenses for the z-deflection of the focal position along an optical axis of the eye. Such systems are for example described in US 2006/195076 A1 or US 2009/131921 A1. On the other hand, systems are also known in which the objective is slowly moved laterally, wherein a fast adjusting lens is used for the z-deflection of the focus along the optical axis of the eye. Such a system is described in DE10 2011 085 046 A1.
While in the initial development years of the LCS some application-related problems, in particular by introducing a liquid interface as a mechanical optical contact between the laser system and the eye were solved, see US 2012/0078241 A1 or U.S. Pat. No. 6,019,472, the integration of the technologies into a device, and to a lesser extent the integration of the technologies into a total workflow or a working environment were in the foreground. In particular, the cooperation between the femtosecond laser and the continued need for a surgical microscope during cataract surgery shows considerable deficits in the systems available on the market.
Most of the currently known systems are independent of the surgical microscope and, due to their size, often stand outside the operating theater later used for the actual implantation of the intraocular lens (IOL). A time-consuming repositioning and transferring of the patient is thereby usually necessary. This deficit was identified only recently and corresponding improvements were suggested:
In DE 10 2010 022 298 A1 and US 2012/316544 A1 it is suggested to couple the femtosecond laser directly and during the course of the surgery permanently with a surgical microscope. However, the required components according to the current state of the art are still too large for this, so that such a system would be too large during the IOL implantation phase, and therefore too restrictive and obstructive for the surgeon.
In WO 2008/098388 A1, a femtosecond laser is inserted under a surgical microscope if necessary, virtually between the surgical microscope and the patient, and is docked to the eye. Here, the surgical microscope and the femtosecond laser virtually operate sequentially and independently from each other. Above all, they are still separate devices.
Furthermore, a number of deficits regarding specific components have been shown in established systems, which negatively affect the quality of the surgery result, the efficiency in the implementation of the surgery or the risk minimization.
A micro objective scan as described in WO 2008/098388 A1 is indeed relatively time-efficient regarding the z-deflection for capsulotomy incisions, or for lens fragmentation as shown in DE 10 2011 085 046. Regarding access incisions, which not only provide a small-scale movement along the optical axis of the eye, but also a small lateral movement of the micro objective, as disclosed in US 2007/173794 A1, this solution is however very time consuming.
In addition, the incision guidance in systems with a fast z-deflection is time-critical for the capsulotomy. While a closed path in a lateral x/y plane does not present a problem for the capsulotomy in fast galvoscan systems, it is safety-critical in systems with a fast z-deflection, where the closing of the path only takes place after some time, and the eye can move during this period. Also with corneal access and auxiliary incisions, the advantage of a fast z-deflection of the laser beam does not take effect, as mainly long lateral paths also have to be covered here.
While the above points relate in particular to systems with pure micro objective scans, a number of improvements for systems with combined micro objective and mirror scan result. Combined scan systems are potentially superior compared to pure mirror scan systems with regard to the incision quality.
The contact elements or patient interfaces currently used are complicated in their handling, expensive to manufacture, have many error-prone components and are often unfavorably dimensioned.
Finally, the OCT signals in currently known systems are also disturbed by many reflections in the system. Furthermore, established OCT solutions also have many error-prone and slow components.